Existing applications enable users to install “plug-in” applications that extend the functionality of the existing applications. Users select and install the plug-ins to obtain the functionality. For example, some existing web browsers have a plug-in architecture enabling users to download plug-ins for execution when visiting certain web pages with the web browsers. The plug-ins are installed locally on the computing device of the user executing the web browser. With the existing systems, however, the user is unable to access the installed plug-ins when browsing the web pages with another computing device. Additionally, with the existing web browser plug-in architecture, the web pages generally remain unaware of the existence or execution of the plug-ins.